Small RNAs are involved in a multitude of biological processes in plants. Based on their origins and precursor structures, small RNAs can be divided into two major classes: microRNAs (miRNAs) and small interference RNAs (siRNAs). Small RNAs are typically 21-24 nucleotide (nt) long, and differ in both biogenesis and biological function. In the pathogenic process, pathogens can either induce or suppress the synthesis of small RNAs, which, in turn, regulate the expression of pathogenesis-related genes to mediate diverse plant-pathogen interactions. The biogenesis and biological functions of small RNAs, together with possible regulation mechanisms underlying the host-pathogen interactions, are summarized in this review,
[1] Baulcombe D. RNA silencing in plants. Nature, 2004, 431(7006): 356-363.
[2] Izant JG, Weintraub H. Inhibition of thymidine kinase gene expression by anti-sense RNA: a molecular approach to genetic analysis. Cell, 1984, 36(4): 1007-1015.
[3] Napoli C, Lemieux C, Jorgensen R. Introduction of a chimeric chalcone synthase gene into petunia results in reversible co-suppression of homologous genes in trans. Plant Cell, 1990, 2(4): 279-289.
[4] Aliyari R, Ding SW. RNA-based viral immunity initiated by the Dicer family of host immune receptors. Immunol Rev, 2009, 227(1): 176-188.
[5] Bartel DP. MicroRNAs: genomics, biogenesis, mechanism, and function. Cell, 2004, 116(2): 281-297.
[6] Lee RC, Ambros V. An extensive class of small RNAs in Caenorhabditis elegans. Science, 2001, 294(5543): 862-864.
[7] Lee RC, Feinbaum RL, Ambros V. The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14. Cell, 1993, 75(5): 843-854.
[8] Fire A, Xu SQ, Montgomery MK, Kostas SA, Driver SE, Mello CC. Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans. Nature, 1998, 391(6669): 806-811.
[9] Zamore PD, Haley B. Ribo-gnome: The big world of small RNAs. Science, 2005, 309(5740): 1519-1524.
[10] Meyers BC, Axtell MJ, Bartel B, Bartel DP, Baulcombe D, Bowman JL, Cao XF, Carrington JC, Chen XM, Green PJ, Griffiths-Jones S, Jacobsen SE, Mallory AC, Martienssen RA, Poethig RS, Qi YJ, Vaucheret H, Voinnet O, Watanabe Y, Weigel D, Zhu JK. Criteria for annotation of plant MicroRNAs. Plant Cell, 2008, 20(12): 3186-3190.
[11] Vazquez F. Arabidopsis endogenous small RNAs: highways and byways. Trends Plant Sci, 2006, 11(9): 460-468.
[12] Bernstein E, Caudy AA, Hammond SM, Hannon GJ. Role for a bidentate ribonuclease in the initiation step of RNA interference. Nature, 2001, 409(6818): 363-366.
[13] Ketting RF, Fischer SEJ, Bernstein E, Sijen T, Hannon GJ, Plasterk RHA. Dicer functions in RNA interference and in synthesis of small RNA involved in developmental timing in C. elegans. Genes Dev, 2001, 15(20): 2654-2659.
[14] 谢兆辉. RNA沉默在植物生物逆境反应中的作用. 遗传, 2010, 32(6): 561-570.
[15] Llave C. Virus-derived small interfering RNAs at the core of plant-virus interactions. Trends Plant Sci, 2010, 15(12): 701-707.
[16] Park W, Li JJ, Song RT, Messing J, Chen XM. Carpel factory, a Dicer homolog, and HEN1, a novel protein, act in microRNA metabolism in Arabidopsis thaliana. Curr Biol, 2002, 12(17): 1484-1495.
[17] Harvey JJW, Lewsey MG, Patel K, Westwood J, Heim-städt S, Carr JP, Baulcombe DC. An antiviral defense role of AGO2 in plants. PLoS One, 2011, 6(1): e14639.
[18] Ding SW. RNA-based antiviral immunity. Nat Rev Immunol, 2010, 10(9): 632-644.
[19] Raja P, Sanville BC, Buchmann RC, Bisaro DM. Viral genome methylation as an epigenetic defense against geminiviruses. J Virol, 2008, 82(18): 8997-9007.
[20] 赵庆臻, 赵双宜, 夏光敏. 植物RNA沉默机制的研究进展. 遗传学报, 2005, 32 (1): 104-110.
[21] Schiebel W, Pélissier T, Riedel L, Thalmeir S, Schiebel R, Kempe D, Lottspeich F, Sänger HL, Wassenegger M. Iso-lation of an RNA-directed RNA polymerase-specific cDNA clone from tomato. Plant Cell, 1998, 10(12): 2087-2101.
[22] Carthew RW, Sontheimer EJ. Origins and mechanisms of miRNAs and siRNAs. Cell, 2009, 136(4): 642-655.
[23] Kim VN, Han J, Siomi MC. Biogenesis of small RNAs in animals. Nat Rev Mol Cell Biol, 2009, 10(2): 126-139.
[24] Chen XM. Small RNAs and their roles in plant develop-ment. Annu Rev Cell Dev Biol, 2009, 25: 21-44.
[25] 许振华, 谢传晓. 植物microRNA与逆境响应研究进展. 遗传, 2010, 32(10): 1018-1030.
[26] Katiyar-Agarwal S, Gao S, Vivian-Smith A, Jin HL. A novel class of bacteria-induced small RNAs
